Understanding the Differences Between Cased Hole and Open Hole Completions

After completing a drilling operation, wellbores must be finished. There are many procedures involved in the whole well completion process. They include casing the wellbore, cementing, plug and perf operations, as well as gravel packing, and production tree installation. Well completion can be done through open hole or cased hole method. Both of these methods have their own applications, benefits, and uniqueness. Which system to employ will depend on factors such as the formation’s characteristics, cost considerations, and technical feasibility.

Cased Hole Completions

Cased hole completions involve running production casing along the well’s entire length and through the reservoir. The system acts as a control mechanism for the safe production of desired hydrocarbons. Also, it serves as a barrier to make sure unwanted gasses, fluids, and solids will not be reintroduced into the wellbore. More information about this system is available at Renegade Wireline Services.

After removing the drilling string, a continuous coupling of casings of various diameters is run into the well at different depths. Then, the casings are secured to the formation through cementing.  Once the wellbore has been insulated from the surrounding formation, the casing should be perforated to stimulate production from the reservoir’s viable portions.  In cased hole completions, the casing controls the production of formation fluids, screening out contaminants. Also, the process improves well integrity, provides better zonal reservoir isolation, and makes it easier to complete several zones within the same well.

Open Hole Completions

In this system, drilling mud of an exact viscosity, weight, and inhibition is utilized for matching downhole conditions. This is meant to prevent the wellbore from caving in on itself by using hydrostatic pressure difference. Following the removal of the drill string, a production casing is inserted into the drilled hole without running through the reservoir.

Cost Complications for Both Systems

The amount of equipment and manpower required for every procedure is the main distinction between cased and open hole completions. Open hole completions only requires casing to be run through the well to the reservoir’s top. This implies cost savings for extra workforce and equipment procurement. Also, the procedure uses special fluids are used to prevent the well from collapsing, it is still a less costly procedure. It is a better option for horizontal wells.

Moreover, cased hole completions involve production casing running through the entire well length, up to the different zones to tap hydrocarbons. Procuring casings, cement, equipment, and manpower required for this procedure can be costly. It is usually best for vertical wells with low formation integrity.

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